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Full text of "Vibration, a better method of placing concrete."

J '2 && 














BETTER METHOD OF PLACING CONCRETE 





A BETTER METHOD 
OF PLACING CONCRETE 



Vibrated 
Concrete 



Vibration 
Equipment 



Test Data 



Proportioning Concrete 
for Vibration 



Recomme 
Practice 



nded 



Vibrated 
Concrete Jobs 



Bibliography 



PUBLISHED BY 



PORTLAND CEMENT ASSOCIATION 

33 WEST GRAND AVENUE 
CHICAGO, ILLINOIS 



TO OUR FRIENDS 
WHO USE CONCRETE: 

Engineers and contractors have reported successful re- 
sults with concrete placed bv vibration. "It improves 

quality." they say. 

Checking by our own research laboratory, state high- 
way departments and leading universities substantiate 
the excellent results reported from the field. Hence this 
booklet to summarize the most recent data on placing 

concrete b) vibration. 

Vibration makes stiff concrete workable. It helps to 
produce dense watertight, durable concrete. As a result, 
it has come into extensive use The U. S. Bureau of Rec- 
lamation, the U. S. Corps of Engineers and many othc 
engineers now sj cify vibration for placing concrete in 
important dams, bridges and other structures. 

Th engine rs specify vibration b< ausc it offers a 

method of reducing the water content oi i concrete mix- 



ture without inci asing the cost oi placing or the cost of 

mat- In son cases these costs actually mav b 

reduc 1. 

Wt I ! that \ou and other men in the construction 
industn want to know more about vibration So, in th i 

booklet, we make rather free use of published data re 

port suits of carefull) control! I tests made to ob- 

tain th< lull ad van t if vibration The data show what 

ration pi disc an improved, economical pla in 
method. 

Your ) rtuular job conditions of course may not 

nit u tO i ali/c II oi the iodic 1 antages oi 

placing by \ibi :ion But \ibrati* promises much. It 

Id help earn on the main outstanding ad ancc 
already I dc in concrete construction. 



Ctt /tCanci (tttf(§t( ((siviuittvH 




;- 



*v 





L%-ifi. slump concrete. 



Two construction views, state highway bridge, Ramona Boule- 
vard, Los Angeles, California. Concrete of iy 2 -in. slump placed 
by vibration in this complicated network of steel. 



VIBRATED CONCRETE 

Why use vibration instead of hand methods for placing 
or puddling concrete? 

Accompanying photographs give the answer. To place 
stiff concrete like that illustrated above (lj^in. slump) 
in forms containing complicated reinforcement, requires a 
mechanical method of puddling it into position. It is 
impractical, uneconomical to place such concrete by hand. 

In short, the mixture must be made to flow into place. 
But it is poor practice to make concrete fluid by adding 
water. It is well known that decreasing the amount of 
water (within the range of workable mixtures) improves 
the strength, durability, watertightness and other quali- 
ties of concrete. Common sense, therefore, decrees that the 
water content should not be increased over that required 
to get the desired quality. 

While improvements in quality are brought about by 
reducing the water content, such reductions produce stiffer 
concrete unless the quantity of cement paste is increased. 
In increasing the paste content, a point is soon reached 
where further increases are less economical than the extra 
effort required to place stiffer mixes. Mechanical vibration 



3 



VIBRATION 




! ve of spade vibrator permits economical placing of stiff, harsh concrete in dam construction. 
Alma, ^ i^onsin. 

of! rs a means of reducing this effort and extends the range 

of practical mixes to include consistencies which cannot 

I plac 1 economical by hand. It also permits harsher 

- that is, concrete containing a Larger proportion of 



n xc 



arse and a smaller proportion of line abrogate. 

( arser gradin in turn, requires less watei Reducing 
the water content th n through stiffer mixes and coarser 
grading— makes possible increases in strength, with cor- 

respondin improvements in other qualities of concrete, 
witi >ut inci ing th< cement requirements. 
Hi 1 • gthi and other improvements in quality, ol 

, iui * the result of vibration itself, hut are possi- 

ble only b sc vibration permits the use of less water 

BENEFITS OF PLACING 
CONCRETE BY VIBRATION 

•h reduction in mixing water made possible by 

\ : the foil' 11)14 benefits . erne 

] [ncn npre \e and fie Ural Strength 



[ncn d densitj d \\ atertighti 

I • • .i rpti i. 

Inerea d resistance to \\ eathenng 



s 



v i r * a t o 



4 



-^-^ -— 




Compacting concrete with spade vibrator at Calumet Sewage Treatment Plant being 
Chicago, Illinois. 



built in 



5. Better bond between successive layers of concrete. 

6. Better bond between concrete and reinforcement. 

7. Less volume change. 

8. Greater economy. 

Earlier removal of forms and earlier finishing with a 
minimum of patching are other advantages often made 
possible by vibration. 

Vibration also helps place concrete of good quality in 
difficult locations, making it more economical than hand 
placing. 

HOW TO GET BEST RESULTS 

A review of investigations to develop fundamental data 
on placing concrete by vibration reveals that the following 
must be considered to obtain maximum benefit from me- 
chanical placement: 

1. The mixture must be as stiff as practicable within 
the limits of placeability. 

2. The sand (fine aggregate) content should be lower 
than required for hand placing. 

3. The vibration should be intense enough to compact 
the mass thoroughly. 



VIBRATION 



VIBRATION EQUIPMENT 

Vibrators producing high frequencies of low amplitude 
have been developed to puddle and compact stiff concrete. 
Most equipment gives at least 3,000 impulses per minute. 
Some produce much higher frequencies. These vibrating 
elements are most commonly used: 

1. Electric motor with an unbalanced member. 

2. Reciprocating cylinder operated by compressed air. 

3. Unbalanced shaft driven by motor or engine. 

■ 

4. Electric magnet pulsator. 

5. Air-driven motor with an unbalanced member. 

6. Gasoline engine with unbalanced fly wheel. 

Electricity, compressed air or gasoline may be used for 
power. 

JOB CONDITIONS GOVERN 
CHOICE OF EQUIPMENT 

The type of vibration equipment required depends 
largely on the conditions of placement. Obviously, equip- 
ment best suited for large, open form work, as encountered 
in dams and heavy retaining walls, is not suitable for thin 
reinforced members or for the manufacture of cast stone 
and other precast concrete products. 

Pulsations of the vibrating element may be transmitted 
directly to the concrete through special devices or indi- 
rectly by attachment to the forms. Job conditions de- 
termine how this should be done. 



TYPES OF VIBRATORS 



Spud vibrator, spade vibrator, platform vibrator, table 
vibrator, form vibrator and vibratory screed are the terms 
most commonly used to designate the various types of 
vibration equipment. Internal vibration designates vibra- 
tion in which the equipment is in direct contact with the 



VIBRATION 



6 




Vibration helping to place quality concrete mix in floor slab for reinforced concrete building 



concrete. External vibration designates vibration in which 
the pulsations are transmitted through the forms. 

SPUD VIBRATOR 

This is a vibrating element attached to a spud — usually 
a short piece of 2 by 4 — which is held against the inside 
faces of forms and on the reinforcement, or which is moved 
about in the concrete. Flexible handles prevent vibration 
from being transmitted to the operator. 

SPADE VIBRATOR 

One type of spade vibrator consists of a vibrating cle- 
ment placed in a watertight, elliptical shell. It is moved 
about in the concrete by means of a long pipe handle. 

Another type consists of an eccentric shaft in a metal 
tube. Power is obtained from a motor-driven flexible shaft. 

Either of these vibrators will operate in wall forms up 
to about 20 ft. high. 

PLATFORM VIBRATOR 

The vibrating element in this equipment is attached to 
a heavy plank or a metal shoe which is placed on top of 
the concrete. Flexible handles are provided. This vibrator 
is used in open forms for dams and similar construction. 



VIBRATION 




Internal vibrator produces smooth 
surfaces against forms. Note dry con- 
dition of top surface in foreground. 
This was compacted with platform 
\ ibrator. 




Placing concrete in deep girders 
through use of spud vibrator. Vibra- 
tion helps get concrete under and 
around reinforcement in such con- 
struction. 



TABLE VIBRATOR 

This type, in which vibrating elements are attached 
to the under side of a table on which molds are placed, 
is used to manufacture cast stone, precast concrete joists 
and other products. The use of gang molds permits cast- 
ing and vibrating a number of products at one time. 

FORM VIBRATOR 

Some vibrating elements may be attached directly to 
the forms with clamps. They have been used on many 
types of structures and for manufacturing concrete piles, 
poles and pipe. The vibrator often is fastened to pipe or 
column forms with an encircling chain which tends to 
extend vibration around the circumference. 

VIBRATORY SCREED 

This is a screed finishing machine— with vibration ele- 
ments attached to the screeds— similar to those used for 
placing concrete pavements. The screeds arc usually heav- 
ier and wider than those on finishing machines not 
equipped with vibrators. 



VIBRATION 



8 



TEST DATA 

This review of research results summarizes data from 
many tests of vibrated concrete. It forecasts the extent of 
improvements possible in concrete when full advantage 
of vibration is obtained. 

It is important to note that this research indicates that 
the relation between water-cement ratio and strength 
holds true for vibrated concrete as well as for hand-placed 
concrete. Tests show that, while higher strengths are 
obtained with vibration, the increases are proportional 
to the decreases in water content. 

Tests also indicate that improved durability and water- 
tightness and decreased absorption also are proportional 
to reductions in water content. 

Thus, vibration imparts no new qualities to concrete, 
except to permit proper placing of mixtures which are 
unworkable for hand methods. 

The test data cover compressive and flexural strength, 
bond with steel, bond between successive layers of con- 
crete, surface hardness, absorption, durability, pressure 
on forms, and air bubbles. From these data certain con- 
clusions also can be drawn regarding volume change. 

COMPRESSIVE AND FLEXURAL 
STRENGTH TESTS 

Vibration permits the use of less water than required 
for hand placing.* Within the range of practical mixes, 
the reduction may amount to 8 or 9 gal. per cu. yd. of 
concrete. This reduced water content increases strength 
about 1,750 lb. per sq. in.; increases modulus of rupture 
about 80 to 180 lb. per sq. in. in concrete of given cement 
content. 

Due to the stiffer mixes that can be used with vibration, 
a given compressive or flexural strength may be produced 

♦"Vibrated Concrete," Journal, American Concrete Institute, June, 1933, Vol. 4, No. 9, 
page 373, by T. C Powers, Associate Engineer, Research Laboratory, Portland Cement 
Association, Chicago. 

9 



V I 8 R A T I O r 



with leaner mixes than are required for hand placing. 

T. C. Powers' report covers tests in which the concrete 
was damp-cured for 28 days and tested damp. 

Raymond E. Davis and Harmer E. Davis also show 
that vibration produces increased strengths because it 
permits less mixing water. In a group of wall sections, 



( 



) 



by using a 



spade vibrator. With a platform vibrator they reduced 
the slump from 6J^ in. (required for hand placing) to 
1 in. These comparisons were made on the basis of equal 
time for placing by hand or by vibration. 

VIBRATED CONCRETE FOR 
PRECAST PRODUCTS 

Following is an interesting comparison of concretes 
suitable for precast products t A l-lJ^-3 mix having no 
slump had a strength of 8,030 lb. per sq. in. at 14 days. 
It could be placed only bv vibration. A 1-1^-1^ mix 
suitable for hand placing under the same conditions, had 
a strength of 6,080 lb. per sq. in. at 14 days. 

A concrete products plant reports increases in compres- 
sive Strength of 100 per cent due to vibration; decreases 
in absorption from 7 per cent bv weight for hand-placed 
concrete to 3 per cent for vibrated concrete.} Another 
advantage reported is that vibrated concrete can be pol- 
ished in 3 da\s after casting. Hand-placed concrete had 

to be cured 7 to 14 days. 

VIBRATED CONCRETE FOR 
PAVEMENTS 

F. H Jack m and \V. F. Kcllcrman** have made tests 
using three different coarse aggregates and two tradings 

•Professor and Instructor, r cctivt of Civil Engineering, Universn >i California 
See Bibliographv : age 31, reference No. 26.) 
•ee Hibliograj age 31. reference No 24 

ibliograpl cc 32, reference 33 

1 Associate Materials Lngincc tivel) U S Bureau < 

Public Roac' W* L, D. C ibliograpl page 3 rc£e« 25 ; 



V I B R A T I O N_ 



10 




Using spade vibrator to place mass concrete made with extra large aggregate, Pine Canyon Dam 
Pasadena, California. 



» 



of sand. They found that they could reduce the slump from 
23 2 i n -, the minimum required to produce the least honey- 
combing with these materials and the ordinary pavement 
finishing methods, to 1 in. by using a vibratory screed. 
The average flexural strength of vibrated concrete slabs 
having the same proportions of cement, fine aggregate 
and water was not reduced when the coarse aggregate 
was one-half part more than used in concrete placed by 
ordinary methods. With some of the materials, the coarse 
aggregate was increased by three-fourths part without 
reducing flexural strength. 

F. V. Reagel* reports similar results from tests made b\ 
the Missouri State Highway Commission. Cores taken 
from vibrated concrete pavement had an average com- 
pressive strength of 580 lb. per sq. in., or 11.8 per cent, 
more than concrete placed in the standard manner. Re- 
ducing the amount of mixing water, without changing 
the amount of cement, made this increase possible. 

V. L. Gloverf reports that the use of vibratory screed s 
made it possible to use 3^2"i n - slump concrete in pavements. 

♦Engineer of Materials, Missouri State Highway Commission, Jefferson City, Mo. (Sec 

Bibliography, page 32, reference No. 29.) 

tEngineer of Materials, Illinois Division of Highways, Springfield, III. .See Bibliography, 

page 32, reference No. 38.) 



11 



VI B R A T I O h 



The finishing machine had heavier and wider screeds than 
usual, with four vibrators on the front screed and two on 
the rear. 

TESTS OF CONCRETE BEAMS 

Flexural tests on concrete beams placed by hand and 
by three different vibration methods and compression 
tests on cores cut from these beams — made by L. W. 
Teller and G. W. Davis* — show that flexural strength 
ranged up to 30 per cent higher for vibrated concrete 
compressive strength, up to 33 per cent higher. These 
increases were brought about by the decreases in water 
content. 



BOND WITH STEEL 

Bond strength of deformed bars was noticeably increased 
by all the vibratory placing methods used in the tests by 

Teller and Da\is Bars were pulled out of the hardened, 
vibrat ! concrete to determine bond strength. There was 
some increased strength with plain bars, but the effect of 

vibration was much less marked. 

Concrete of the same water content was used in the 
spc lmens placed by hand and those placed by vibration. 
There was a noticeable amount of honevcomb around thi 
bars in the hand-placed specimens. The tests indicate that 

the better bond between vibrated concrete and steel was 
du. to the more intimate and uniform contact produced 
. vibration These tests were too few in number to show 
what increases in bond strength can be expected lor other 



onditions 



BOND BETWEEN SUCCESSIVE 
LAYERS OF CONCRETE 

\ i brat ion helps provide a better bond between nev 
c QCretC and concrete which has been in place several 

Kin • . W \dU ^inccr J cits, ropcuivch, U S bureau of 

Pub • ^Js, Washington, D ' Sec biMiogra , page 31, reference No 17 ) 



V l b f> A T i O N 



1? 







Platform vibrator is particularly adaptable to placing quality concrete in open form work 



days, according to the Davis and Davis* tests. Even when 
materials have segregated, with coarse aggregate at the 
bottom of the new layer, vibration will re-mix the con- 
crete and produce better bond. 

SURFACE HARDNESS TESTS 

Construction methods must not impair the hardness of 
concrete pavement surfaces. The tests made by Jackson 
and Kellermant with a vibratory screed included studies 
of pavement wear. Their tests indicate that surface hard- 
ness of pavements is not adversely affected when the con- 
crete is compacted with a vibratory screed. 

It should be realized that in these tests the consistency 
of the concrete was suitable for the materials and the 
equipment used. It is likely that only small amounts of 
mortar and water were brought to the surface and that 
most of this material was removed in the finishing process. 
An excess of mortar on the surface might cause scaling. 
It is important, therefore, to use mixes suitable for the 
methods of construction and thus avoid this possible 
difficulty. 



*Sce Bibliography, page 31, reference No. 26 
fSce Bibliography, page 31, reference No. 25 



13 



V I B R A T I O I 




Using vibratory screed to compact low-slump concrete as it is placed for pavement construction 



In the tests reported by Glover,* while some of the 
sections exhibited signs of scaling, those sections where 
the mixes were most suited to the vibratory equipment 
did not exhibit this tendency to any great extent. 

ABSORPTION TESTS 

The absorption of vibrated concrete is perceptibly less 
than for hand-placed concrete of the same mix and water 
content, according to the Teller and Davisf tests. The 
specimens tested were 10 to 12 months old. These were 
dried, put in water, and absorption determined after 
periods of 1 to 140 days immersion. For vibrated concrete 
made with ordinary aggregates, such as gravel and crushed 
stone, absorption was reduced as much as 32 per cent for 
short periods and 41 per cent for long periods of im- 
mersion. 

The reductions in absorption were not due to changes in 
the mix. Therefore, it is likely that the vibratorv action 
brought water to the surface which was removed in fin- 
ishing. This would have the same effect as using less 
water for mixing. 

•See Bibliography, page 32, reference No J8. 
fScc Bibliography, page 31, reference N'o 17. 



VI B R A T I O N 



14 




Platform vibrator compacts stiff concrete containing a^maximum amount of coarse aggregate, 
Chute a Caron Dam, Kenogami, Quebec, Canada. 



Absorption of concrete placed with a vibratory screed 
was less than for standard finished concrete in the tests 
made by Jackson and Kellerman*. This was due to the 
lower slump and smaller amount of mixing water used in 

vibrated concrete. 



DURABILITY TESTS 

How does vibration affect durability? That is a natural 
question since the durability of concrete or its resistance 
to weathering is extremely important. 

In general, the least absorptive concrete is the most 
durable. It has a minimum amount of contained moisture 
that will exert pressure upon freezing. It permits the least 
leaching due to wetting and drying. Therefore, when 
vibration produces denser concrete of lower absorption 
through reducing the amount of mixing water, it also 

makes more durable concrete. 

An accelerated durability test, subjecting specimens to 
alternate freezing and thawing in a refrigerator, is quite 
widely used. Powersf reports results of this test on vi- 
brated concrete made with 4, 5 and 6 sacks of cement per 



*Scc Bibliography, page 31, reference No. 25- 
|See Bibliography, page 31, reference No. 27. 



15 



VIBRATION 



cu. yd. The specimens withstood 110 cycles* of freezing and 
thawing without showing signs of trouble, indicating a 
high degree of resistance to weathering under the most 
trying conditions. 

Although it is difficult to establish a definite relation 
between results of this test and the durability of concrete 
under a given set of exposure conditions, the following 
demonstrates the severity of the test: 

J 

Concrete of ordinary quality — which had withstood 
severe exposure for 20 years in the northern states, with- 
out even surface blemishes — showed heavy scaling and 
disintegrated when put through 20 to 40 cycles of freezing 
and thawing in the refrigerator. 

The durability of concrete is improved by vibration, 
a ording to Davis and Davis. t They exposed concrete 
specimens to freezing and thawing; then tested for com- 
pressive strength. Their results show that the strength 
of internallv vibrated concrete is less affected bv the 
accelerated test than is the strength of hand-tamped 
concrete. 



VOLUME CHANGE 

Direct test data are not available on the effect of vibra- 
tion on expansion and contraction. However, on account 
of the changes that can be made in the mix, vibration 
promises a method of producing low-shrinkage concrete, 
ince vibration permits stiffer, harsher concrete, leaner 
mixes can be used with less water than required for hand 
placing. These changes in the mix reduce shrinkage. 

It is possible that placing concrete by vibration will 
reduce shrinkage to one-half that which occurs in hand- 
placed concrete. J This statement is made on the basis of 
data on factors known to affect volume change. 

♦Since this report was published, the tests have been extended to 175 cycles with no 
destructive action. 



See 



Bibliography, page 31, reference No 26. 
Bibliograph page 31, reference No 27. 



VIBRATION 



16 




Hand screed equipped with two vibrating units for use in placing stiff concrete for pavements 



PRESSURE ON FORMS 

Does placing by vibration exert greater pressure on 
forms? Are stronger forms required? Tests made bv L. W. 
Teller* on columns 12 ft. high, 2 ft. wide and 8 in. thick 
answer these questions. Vibrators were attached to bat- 
tens on the forms. Pressures were measured with four soil 
pressure cells inserted at intervals in one side of each form. 

For concrete of lj^-in. slump placed by vibration, the 
maximum pressure 1 ft. from the bottom was llj^ 1°. per 
sq. in., or the equivalent of the fluid pressure of the full 
column of concrete. Hand-spaded concrete, with 7j^-in. 
slump, exerted little more than one-half this pressure. 

With hand placing, pressure increased h\ drostatically 
up to a certain value, after which it decreased, the maxi- 
mum pressure increasing with the fluidity of the concrete. 
For vibrated concrete, fluidity was retained so long as 
vibration continued. 

Similar results are indicated for internal vibration. The 
portion of the mass which is in agitation exerts the same 
pressure against the forms as a liquid of the density of 
concrete, according to Davis and Davis. They state that, 



*Senior Engiaccr of Tests, U. S. Bureau of Public Roads, Washington, D. C. (See Bibli- 
ography, page 30, reference No. 11.) 



17 



VI 8 R A T I O N 




,^\, ng i edwtl hratOfs as it is plait-il around piling in dam consiruCtlOO. 



)n rin be rau of placing and the mass to be vibrated 
a m mium prcssun of about } or 4 lb pel sc| m nia\ be 

• I in ordin building co itruction.* However, 
vhcr< placii is vet) rapid as in column construction 

rr< | idingly higher pressures ma) be encountered 
Und most tions greater pressure is exerted bj 

• be vibrated, so bums should be designed foi 

his more S rvic< 



AIR BUBBLES 

It is ; rt< that vibration sometimes increai the 

f air bubbl the surfa< of e<>: crct< Y\ hi) 



s: 



brated I actuall) < titain 1 s air than hand 

placed < th< air oil it to lar i bubbl alon 

the I • -irfa i I is d >re not abb 

I )i lt> v h air bubbl in ag tc pipe i 

the Montreal Water h ard was ac unp for in the 

bra- i that v I > light Mor< pow< I iribratori 

o\ ic the iilfu r\ It was foi that ss p.* c 

t< • retain * * an * > >thcr jobs sb< tha 

csj sand i i rtar I ds to mere sc Mjrfa bubbles. 



• 



mptn M| 















11 



A—~— 






u 

H 



v i i / i o ••_ 



11 



PROPORTIONING CONCRETE 
FOR VIBRATION 



r 



To get the best results with vibration, the mixture 
must be proportioned so the concrete is suitable for plac- 
ing with the equipment provided and under the conditions 
of the job. Concrete having a slump of 4 in., or more, 
seldom is suitable. Suffer concrete can be used to advan- 
tage in nearly every case. 

Simply reducing the amount of mixing water in a mix- 
ture suitable for hand placing does not provide a mixture 
suitable for placing by vibration. Such a mixture usually 
contains more mortar than necessary, and this proves to 
be a disadvantage in work such as pavements, where 
excess mortar may work to the surface, scale and wear ofT. 

Full advantage of vibration is obtained when the pro- 
portion of coarse aggregate is increased and the quantity 
of water decreased. 

HOW METHOD OF PLACING AFFECTS 
PROPORTION OF SAND 

Fig. 1, page 20, from Powers' report* shows that stiff 
mixes, having a minimum of sand, are most suitable for 
placing by vibration. The consistency of the concrete suited 
the method of placing used in these tests. 

For concrete made with 5 sacks of cement per cu. yd. 
and the aggregates used in Powers' tests, a mixture con- 
taining 36 per cent sand proved to be best for hand plac- 
ing. Vibration permitted less mixing water with these 
same proportions of materials and increased the strength 
1,250 lb. per sq. in. 

Powers found it possible to use less sand; reduced it to 
28 per cent, the practical minimum (with these materials) 
for placing by vibration. This permitted further reduction 
in water content and effected an additional gain in strength 
of 900 lb. per sq. in. 



*See Bibliography, page 31, reference No. 27 



19 



VIBRATION 



\ 



Increases in strength developed in Powers' tests were 
not brought about directly by reduction of the sand factor, 
but were due to the smaller amounts of mixing water 
required with the lower sand contents. 

The amount of sand for proper placing by vibration 
will vary with grading and character of the aggregates, 
richness of the mix, and conditions of placement. 

Unlike hand-placed concrete, vibrated concrete does not 
show a falling off in strength when the sand percentage is 
extremely low. See Fig. 1. There apparently is a lower 
limit of sand percentage for vibrated concrete, but it must 
be determined by behavior of the concrete under vibra- 
tion. The lower limit has been exceeded when coarse 
material, which will not be absorbed by the mixture under 
vibratory action, lies loosely on top of the mass. 

PLASTIC CONCRETE 

For complete compaction concrete must be plastic. For 
hand placing, the mixture must be so proportioned that 



1000 



CT 

a 

I 



6000 



cr 

c 

In 

V 



if) 
if) 

<u 

Ol 

E 

o 



5000 



4000 



3000 




(0 






2000 



^-Typical Relationship 
for Hand-Placed Concrete 
50 socks percu.yd. 



Derived Curves 

I L 



20 



22 24 26 28 30 32 34 36 38 40 42 

Per cenl Sand bywiof Total Aqgreqa+e 



44 46 



Fig. 1 — Relation between compressive strength and percentage of sand for 



vibrated concrete. 



V I B R A T I O N^. 



#» W * 



20 



the concrete is plastic when it goes into the forms. For 
mechanical placing, the mixture must be so proportioned 
that, with vibratory action, the concrete becomes plastic 
after it is placed in the forms. A hardened mass of con- 
crete, free from aggregate pockets and honeycomb, can be 
obtained only when the mixture is plastic when placed 
or is made plastic by vibration. 

Definite proportions cannot be specified for vibrated 
concrete any more than they can be specified for hand- 
placed concrete. However, some of the variables to be 
considered are the characteristics of the materials, size and 
shape of forms, distribution of reinforcement, and type 
and power of vibrating equipment to be used. 

Mixes should be designed for vibration by the method 
used for hand-placed concrete — that is, the water-cement 
ratio should be selected to meet the required exposure or 
strength and aggregate proportions determined by trial 
mixtures. 



RECOMMENDED PRACTICE 

Due to the wide variety of working conditions it is 
almost impossible to prepare a complete manual on placing 
concrete by vibration. However, in view of available data 
and the experience of qualified observers, it is possible to 
present the following practices which are known to pro- 
duce good results and which may be applied under a fairly 
wide range of conditions: 

1. Vibration should have a frequency of at least 3,200 
impulses per minute. 

2. Vibration should be of sufficient intensity and 
duration to cause flow or settlement of the con- 
crete and complete compaction. Large masses per- 
mit larger aggregates and stiffer concrete, but also 
require more powerful equipment to overcome the 



inertia of the mass. 



21 



VIBRATION 




3. Over-vibration, especially of mixtures chat are too 
wet, may cause segregation and should be avoided. 
Where mixtures are properly proportioned, there 
should be no segregation unless the vibration is 
unduly prolonged. 

4. A sufficient number of vibrators should be provided 
to permit compaction of each batch before the next 
batch is delivered, and without delaying the 
delivery. On some projects, vibrators of several types 
can be used to advantage. Thus, in large, open form 
work, spud or spade vibrators are needed near the 
form while platform and spade vibrators can be 
used in the central portion of each lift ot concrete. 

5. Vibration should be applied directly to the con- 
crete wherever possible. 

6. Vibration through the forms should be permitted 
onlv in those sections where the action will nor 

- 

disturb partialh hardened concrete. When attached 
to wall forms, the vibrators should be raised in 
about 3-ft. lift- This may vary with the power of 
the equipment. 

7. Vibration should be applied at the point of deposit 
and in the area of freshly deposited concrete. 

S. Concre: houJd be placed in layer* o( uniform 

thickness. 

9. Vibration should not be used to cau^c concrete to 

rlow over Long distances in the forms Where thi 
practice is permitted borne separation ot materia 
is almost certain to occur. In long sections, th 
concrete should be placed in the form- at closel 
spaced intervals to prevent excessive flowing. 

10. With internal vibration, the apparatus should be 
so operated that the vibrating element do not 



VIBRATION 



22 




(Jting vibratory <>cr d to pUct Concrete f< Nap W« lir . I h, M 



penetrate through the la r I fresh ( rctc a 

disturb partialk hard* i I in th I 

bel 



in' 



II Inrcni.il vibrators pull them k hh the 
of concrete Therefore, the) should i : 

into flu m.iss too rapidl) Likewise, the 

he withdraw n slow k to pre\ form. in 



« 



12 ro secure c\ n surfaces, free fi »m i regatep k 

or hoiK-vionih. flu mcretC sh< 1 he forked or 

spaded bj ban I in all corners and at les (A I c 
forms gnd aloi form suri i whiJ it is r" 

\ i bra ted 

H \t all time the qua:: tit v I nixing water sfa 

he the least amount that will pf e the rcquir 

consist ic> and the proj ion >ul 

he the lowest that will ijive ( rctc t the v rk 

abilit) tie*, isar) tor placing with the equipment 

provided While the concrete shoi h Fa 

possible, it should not K vo dry a^ t produce 
honeycomb or aggre : pockets nor wet 

produce a fluid condil I the top the l< r 



23 



V ■ » A T O 




Vibrator attached to steel beams places cinder-coo 
Office. Philadelphia, Pennsylvania. 



Crete in floor arches and around beams. Post 



14. Proper grading of aggregate is just as important 
as for hand-placed concrete. While more coarse 
material may be used in vibrated concrete, it is 
essential that the sand contain sufficient lines for 
workability and to prevent separation of water 
from the mass. 

15 Forms should be tight. Vibration increases pressure 
and extra precautions should be taken to prevent 
leakage of mortar which may cause sand streaks 
and honeycomb Tongue-and-groove lumber helps 
in th respect. Forms should be designed for the 
more severe conditions of vibration — higher pres- 
sure- and greater strain on ties and supports. 

16. Close supervision is required at all times to assure 
thorough vibration of all sections. Operator- 
should watch for stone pockets, which may occur 
at adjoining loads of concrete, and should be in- 
structed to redistribute materials in such areas by 
moving vibrators through them. Areas which are 
skipped or not given enough vibration to compact 
the mass completely ma\ prove to be poorer con- 
crete than that properly placed by hand. 



VI E RATIO 



24 





Vibrator attached with encircling Placing concrete by vibration at Pine Canyon Dan. 
i hain to form for concrete pipe. 



VIBRATED CONCRETE JOBS 

The following summaries of technical press reports on 
projects where concrete was placed b) vibration shov 
that mechanical placement is adaptable to a wide varict) 
of concrete construction. Bibliography references listed 
with each brief description give more detailed discussion 
of the methods used. 

CALDERWOOD DAM, TENNESSEE 

Platform vibrators used. Aggregates graded up to 6 in. Concrete 
Jumped from 4-cu. yd. buckets. Compaction of batch secured in le> 
than 5 min., using two or three vibrators each handled by tv men, 
starting at edges of pile and working toward peak as sides slumped 
down. (See Bibliography, page 30, reference No 6.) 

CHUTE A CARON DAM, QUEBEC 

Two platform vibrators compacted 4-cu. yd. batches in about 3 
min. Hand placing would have materially reduced amount of coarse 
aggregate and hence the yield, especially with such large 1 ches. 
Vibration also prevented accumulation of excess water on top of each 
layer. (See Bibliography, page 30, reference No. 7.) 

PINE CANYON DAM, CALIFORNIA 



ra 



Spade and platform vibrators used. Concrete had water-cement 
tio of 0.88 with slump about : > 4 in., and was dumped in 4-cu. J 



55 



V I B 



A T I O I 




Showing how form vibration is used to place quality mixes for precast concrete piles. 



batches. Crew of six men and a foreman, with two spade vibrators 
and one platform vibrator, compacted concrete at consistent rate of 
50 cu. yd. per hr. No seepage occurred between lifts of concrete, 
indicating good bond between layers. (See Bibliography, pages 31 and 
32, references Nos. 16 and 37.) 

OGDEN AVENUE GRADE SEPARATION, CHICAGO 

Form vibrators, attached by means of encircling chain, used on 
columns. (See Bibliography, page 32, reference No. 30.) 

HAMILTON DAM, TEXAS 

Form vibrators used on counterforts. (See Bibliography, page 32, 
reference No. 30.) 

POST OFFICE, PHILADELPHIA 

Vibrator attached to steel floor beams to place cinder-concrete in 
floor arches and around beams. Beams spaced 6 34 ft. apart, each 
vibrated 15 sec. (See Bibliography, page 32, reference No. 36.) 

EXPERIMENTAL ROAD, ARLINGTON, VIRGINIA 

U. S. Bureau of Public Roads used standard double-screed finishing 
machine equipped with two vibrators on front screed and one on rear 
screed. (See Bibliography, page 31, reference No. 25.) 

SCHUYLKILL BRIDGE, PHILADELPHIA 

Spud vibrators on decks and form vibrators on columns. (See 
Bibliography, page 32, reference No. 30.) 



VI B R A T I O N 



26 






* * 



>.* 



^ • 






. 



j - 



i - 



A f 



r *J 










Spud vibrator in action, placing stiff concrete in slab that is rather heavily reinforced 



i 



KOON DAM, MARYLAND 

Platform vibrators used. Exceptionally smooth surfaces free from 
honeycomb reported, although very harsh mix was used. (See Bibli- 
ography, page 30, reference No. 16.) 

ARIEL DAM, WASHINGTON 

Vibrator consisted of gasoline engine equipped with an eccentric 
flywheel and mounted on a steel shoe. Concrete placed with 2-cu. yd 
buckets and spread in 12-in. layers. (See Bibliography, page 30, refer- 
ence No. 12.) 

16TH STREET VIADUCT, CHICAGO 

Spud vibrators especially effective in placing concrete under and 
around deep I-beams and in heavily reinforced slabs. (See Bibliography, 
page 32, reference No. 30.) 

CAST STONE 

Dextone Co., New Haven, Conn., use vibrator table and spade 
vibrator. Strengths much higher than under former methods are 
obtained. Absorption reduced. Products can be polished in 3 days 
whereas formerly it was necessary to wait 7 to 14 days. (See Bibli- 
ography, page 32, reference No. 33) 

HIGHWAYS IN MISSOURI 

Missouri State Highway Commission used a finisher with three 
vibrators on front screed and two on rear screed. Screeds wider and 



27 



V I B R A T I O 



heavier than usual. Stiff consistency was essential. Standard mixture 
contained too much mortar which could not be corrected by using 
less water. Increased proportion of coarse aggregate and lower sand 
factor gave best results. (See Bibliography, page 32, reference No. 29.) 



PRECAST PILES FOR MICHIGAN STATE 
HIGHWAY DEPARTMENT 

Spud vibrators used. It was advisable to nail cleats over top of forms 
about every 4 ft. and require operator to work in each cell successively. 
This prevented honeycomb in areas that might otherwise be skipped. 
Slump of \ x /i in. used. Driving strength developed in 3 or 4 days. 
(See Bibliography, page 32, reference No. 32.) 

TRAFFIC CIRCLE, CAMDEN, N. J. 

A 4-in. oak plank — 14 in. wide, 12 ft. long and equipped with two 
vibrators — used as screed. Five men could finish 1,000 lin. ft. of pave- 
ment per day, while it required eight men to finish 600 ft. without 
vibration. (See Bibliography, page 31, reference No. 21.) 

PRECAST PIPE FOR WATER BOARD, MONTREAL 



Job required 60,000 ft. 
steel form, 16^ ft. long, 
Pipe cast vertically. (See 



of 36-in. pipe. Four vibrators attached to 
were operated continuously during filling. 
Bibliography, page 32, reference No. 34.) 



BRIDGE DECK SLABS, CHICAGO 

Precast slabs, $% in. thick, 56 to 102 sq. ft. in area, used on Clark 
St. and Wabash Ave. bascule bridges. Spud vibrators used. (See 
Bibliography, page 30, reference No. 10.) 

GEORGE WASHINGTON BRIDGE, NEW YORK 

Spud vibrators on decks. (See Bibliography, page 32, reference 
Mo. 31.) 



BAYONNE BRIDGE, NEW JERSEY 

Spud vibrators on decks. (See Bibliography, page 32, reference 
No. 31.) 



MANISTEE BRIDGE, MICHIGAN 

Spud, spade and platform vibrators used experimentally by Michi- 
an State Highway Department. (See Bibliographv, page 32, reference 
No. 32.) 



VI e RATION 



28 




I n floor slab construction, vibration helps to compact stiff concrete under and around reinforcemen 



PILES FOR BRIDGES, OCEAN CITY, N. J. 

Welded steel forms with vibrators attached used in casting 1,200 
piles. A very stiff mix, with only 4 gal. water per sack of cement, was 
used. Vibrators operated continuously during concrete placing. (See 
Bibliography, page 31, reference No. 20.) 

PRECAST PILES FOR HARBOR DEPARTMENT, 
LOS ANGELES 

Pneumatic hammers used on side forms gave higher strengths than 
when concrete was placed by hand. (See Bibliography, page 30, 
reference No. 5-) 



BIBLIOGRAPHY 



'/< 



1. "Concrete Ships Constructed by U. S. Shipping Board," b 

Walter R. Harper. 

Proceedings, American Concrete Institute, 1922, Vol. 18, page 83 

2. "Constructing Concrete Roads h\ Vibration." 

Engineering News-Record, January 1, 1925, Vol. 94, No. 1, page 26. 

3. "Tests of Vibrolithic Concrete," by L. W. Teller and C. E. 
Proud ley. 

Public Roads, April, 1926, Vol. 7, No. 2, page 36, and October, 
1927, Vol. 8, No. 8, page 179. 



29 



V I B R A T I O 



4 



13- 



14. 



15. 



16. 



"Arthur Kill Bridges Paved with Joggled and Vibrated Concrete." 
Engineering News-Record, September 20, 1928, Vol. 101, No. 12, 
page 427. 



5. "Improved Asphalt Treatment for Concrete Piles in Sea Water," 
by G. F. Nicholson. 

Engineering News-Record, Julv 18, 1929, Vol. 103, No. 3, page 95- 



6. "Exceptionally Dry Concrete Used on Two Large Dams." 

Engineering News-Record, October 24, 1929, Vol. 103, No. 
page 640. 



17, 



7. "Concreting Methods at Chute a Caron Dam," by I. E. Burks. 

Proceedings, American Concrete Institute, 1930, Vol. 26, page 315- 

8. "Vibrated Concrete," by E. Treves. 

Le Genie Civil (France), June 28, 1930, No. 2498, page 636. 

9- "Some Tests of Concrete Masonry Units Cured with High Pressure 
Steam," by P. M. Woodworth. 

Proceedings, American Concrete Institute, 1930, Vol. 26, page 504. 

10. " Precast Light-Weight Concrete Slabs Solve Bridge Floor Problem . ' ' 

Concrete, January, 1931, Vol. 38, No. 1, page 15- 

11. "The Effect of Vibration on the Pressure of Concrete Against 
Formwork," by L. W. Teller. 

Public Roads', March, 1931, Vol. 12, No. 1, page 11. 



12. "Ariel Dam 

Engineering 

page 435. 



An Example of Modern Dam Construction Practice. ' ' 
News-Record, March 12, 1931, Vol. 106, No. 11, 



"Large-Span Reinforced Concrete Bridges." 

Concrete and Constructional Engineering (England), June, 1931, 
Vol. 26, No. 6, page 385- 

"The Physical Properties of Cast Stone," by John Tucker, Jr., 
G. W. Walker, and J. Arthur Swenson. 

Journal of Research, U. S. Bureau of Standards, December, 1931, 

Vol. 7, No. 6, page 1061. 



Concreting the Calderwood Tunnel," by W. R. Johnson. 
Proceedings, American Concrete Institute, 1931, Vol. 27, 
1189. 



page 



"Precise Concrete Control at Koon Dam." 

Engineering News-Record, December 31, 1931, Vol. 107, No. 27, 
page 1024. 



VI B R a t i o N 



30 



17. "The Effect of Materials and Methods of Placing on the Strength 
and Other Properties of Concrete Bridge Floor Slabs," by L. W. 
Teller and G. W. Davis. 

Public Roads, December, 1931, Vol. 12, No. 10, page 237. 

18. "Formwork and Concreting Methods on Monolithic Sewer," by 
Harold L. Andrus. 

Concrete, March, 1932, Vol. 40, No. 3, page 12. 

19. "The Segregation of Water in Concrete Placed in Deep Forms," 
by F. H.Jackson and W. F. Kellerman. 

Public Roads, June, 1932, Vol. 13, No. 4, page 64. 

20. "Efficient Pile-Casting Yard for Highway Bridges." 

Engineering News-Record, December 22, 1932, Vol. 109, No. 25, 
page 743- 

21. "Stronger Concrete Pavement by Rapid Tamping," by C. t 
Myers. 

Engineering News-Record, June 23, 1932, Vol. 108, No. 25, page 

894. 



22. "Precast Light-Weight Concrete Slabs Placed on Capitol Dome. 

Concrete, December, 1932, Vol. 40, No 12, page 9. 

23- "Chimneys at Battersea Power Station." 

Concrete and Constructional Engineering (England), April, 1933, 

Vol. 28, No. 4, page 238. 






24. "Mixtures for Vibrated Concrete in Production of Burial Vaults, 
by W. G. Kaiser. 

Concrete, July, 1933, Vol. 41, No. 7, page 13- 

25. "Vibration and Delayed Finishing Improve Pavement Concrete, 
by F. H.Jackson and W. F. Kellerman. 

Public Roads, October, 1933, Vol. 14, No. 8, page 129, 
Proceedings, American Society for Testing Materials, 1933, ab- 
stracted in Concrete, August, 1933, Vol. 41, No. 8, page 8. 

26. "Compaction of Concrete Through the Use of Vibratory Tamp- 
ers," by Raymond E. Davis and Harmer E. Davis. 

Journal, American Concrete Institute, June, 1933, Vol. 4, No. V, 

page 365- 

27. "Vibrated Concrete," by T. C. Powers. 

Journal, American Concrete Institute, June, 1933, Vol. 4, No. 9, 

page 373- 



31 



V I B R A T I O 



28. 'The I r o£ Vibrators in the Manufacture of Concrete Products, 
bv Miles X. Clair. 

Journal, American Concrete Institute, June, 1933, Vol. 4, No. 9, 
page 3 S3 

29. "Vibratory Finishing Machine for Concrete Pavements," by 
F. V. Reagel. 

Journal, American Concrete Institute, June, 1933, Vol. 4, \o. 9, 
page 391. 

30. High Frequency Vibratory Machines for Concrete Placement, 
bv M. I. McCartv. 

Journal, American Concrete Institute, September-October, 1933, 
Vol. 5, No. 1, page 49. 



31. Placement of Concrete by Mechanical Vibration," by A W 
Munsell. 
Journal, American Concrete Institute, September-October, 1933, 
Vol. 5, No. 1, page 54. 



32 



33. 



Vibration on Michigan Br ge Work, by A. C. Beckelman. 
Journal, American Concrete Institute, September-October, 1933, 
Vol. 5, No. 1 page 57. 

Vibration Equipment in Cast Stone Plant, by George B. Picko: 
Journal, American Concrete Institute, September-October, 1933, 
Vol. 5, No. 1 page 59. 



34. Fabricating 36-Inch Reinforced Concrete-Steel Cylinder Water 
Mains," by J. F. Brett. 

Journal, American Concrete Institute, September-October, 1933, 
Vol. 5 \ 1, page 61. 



35- 



Vibration in Making Roof Deck Slabs, bv A. B. Shenk. 
Journal, American Concrete Institute, ^ptember-October, 
Vol. 5, No. 1, page 63- 



1933, 






'Clamper :o Steel Buil ng Frame, Electric Vibrators Produce 
Dense Cinder-Concrete for Floor Arches and Firep- >ohng 
Construction Methods, November, 1933, Vol. 15, No. 11, page 24 



3 



\ :brating Concrete at Pine Canvon Dam, by B. Morris. 
Journal, American Concrete Institute, March-April, 1934, \ o\. 
No 4, page 305. 



5, 



3 X "Vibrates Concrete Pavements. 

Emgmeerimg News-Rccvni, April 26 
1934, page 561. 



1934, page 5-- and V J, 



VIBRATION 



32 



T-J- SM ft-M 



■•.' 



X? 



QUALITY CONCRETE 

B E AUTY 
STRENGTH ECONOMY 

DURABILITY 

R1CIDITY ADAPTABILITY 

WATERTICHTNESS 

RESISTANCE TO WEAR 

FIRE RESISTANCE 






INSPECTION 



CURING 



PLACING 



PLASTICITY 



WORKABILITY 



MIXING 



CONTROL 



PROPORTIONING 



WATER CEMENT RATIO